Starch coating composition



Patented May 30, 1933 UNITED TATE B. SOHUL'IE,

- PANY,

PATENT OFFICE OI MADISON, WISCONSIN, ASSIGNOR TO BURGESS BATTERY (DI- Ol' MADISON, WISCONSIN, AOORPORATION OF WISCONSIN STABCH COATING OOEPOSI'IION Ho Drawing. Original application filed July 6, 1928,

Serial in. 890,885. Divided and this application filed November 8, 1929. Serial No. 405,848.

This invention relates to coating and coating compositions, and more particularly to a coating composition formed b a starch suspension in water, the method or making such suspension, and a product made with such starch suspension.

This application-is a division of my 00- pending application Serial No. 290,885 filed July 6, 1928; and the claims'of this appl1 cation are directed to a dr cell part tion having a coatin of the coating composition herein describe In the present inventionI provide a suspension of starch in water which may be used to coat objects with a uniform layer of adherent and tough ungelatinized starch, and which is particularly useful in coating paper dry cell liners. I,

In the manufacture of a dry cell of the paper-lined type it is desirable to. have an even coating of starch or.other elatinizable cereal on such paper liners priorto the assembling of the cells. Because of the manufacturingldifiiculties caused by gelatinized starch, the cereal the assembling of the cell. The gelatinized starch is sticky and slippery and diflicult to apply evenly to the liner. After the cell is assembled the gelatinizable cereal is gelatinized by the zinc chloride in the cell.

It is difiicult, however, to form a suspension of ungelati'nized starch in water, 'due 7 to its tendency-to settle. I have discovered a method of suspending such cereal inwater so that there is little tendency for'settling and the suspension formed will coat dry cell liners evenly with a hard coating which may be handled during manufacturing opera- 40 tions.

Throughout the specification and claims I use starch in its generic sense and include all starch containing powders which gelatinize on cooking, on'contact with zincchloride, but not in cold water. Such materials is not gelatinized before heated to, near .ly. From 30% may be substituted for corn starch in dry cell manufacture.

When a starch is suspended in cold water the suspensionmust be constantly agitated to prevent the starch from settling out. If

a sheet of porous paper or other bibulous liner, such as is used in certain types of dry cells, is dipped into such a suspension, it becomes coated with ,a. layer of starch; On drying, the starch rubs off easilybecause of the absence of a binder and absence of gelatim'zation of the starch in cold water. A liner coated in this way is objectionable for dry cell manufacture.

have discovered that it is possible to make a mobile stable sus ension of starch in water by having a sma amount of suitable colloid, such as gelatinized starch,v resent in the water suspension. The co oid prevents the rapid settling of the suspension and binds the particles together on the dipped article so that the dried coating is firm and may be handled. The dip isliquid in nature and is not pasty.

To make the starch suspension I first make a water solution of a colloid which is mobile at ordinary tem erature. Glue and agar-a ar may be used or this puqiose, but I pre er to use gelatinized starc The starch may be elatinized in a number of ways, but I pre er to gelatinize it by water boiling. The colloid solution should not contain more than 2% of the gelatinized starch or; it becomes too thick and past for use. I prefer using between 0.5% an 1.5% of gelatinized starch and in onze embodiment of my invention I use about 0.

After the starch is gelatinized the solution is cooled to room temperatures and the starch to be suspended is stirred in thorought of corn starch 'ves' a range of suspension which may be for dipping dr cell liners or it maybe used to dip coies as described in the co-pending application Serial No. 290,761, filed July 6, 1928, of my co-worker, Wayne B. Staley (now Patent N o. 1,760,090, granted May 27, 1930). I prefer usin a solution containing from to o starch when dipping dry cell liners therein, such liners consisting of sheets of soft absorbent paper. The water and colloid suspending solution preferably contains from 0.5% to 1.5% of colloid such as gelatinized starch. Part of thestarch may be replaced by glue, for example: A suspension containing 35% to 45% of starch may contain 0.2% to 0.4% of gelatinized starch and 0.7% to 0.5% of glue.

I have further found that if ammonium chloride is dissolved in the water containing the colloid and suspended starch, it decreases. the viscosity of the colloid solution so that it becomes possible to suspend a greater quantity of starch therein without having the suspension become pasty. In a suspension containing from 30% to of raw starch and 0.5% to 1.5% of gelatinized starch, it is possibleto dissolve from 5% to 15% ammonium chloride. This ammonium chloride is necessary in a dry cell and thus it becomes possible to introduce it atan advantageous place. v

The starch thus introduced into a dry cell is eventually gelatinized by the zinc chloride introduced into or formed by the reaction in the cell. Ordinary corn starch is somewhat more resistant to gelatinization by zinc chloride than flour, potato starch, and some other starches. In order to hasten this gelatini'zation after the cell is assembled, it has been found advantageous to add a small amount of zinc chloride to the starch suspension. The amount is too small to cause gelatinization, usually about 3 percent.

The paper or'other bibulous dry cell liner is dipped into the starch suspension and then I claim:

1. As a new article of manufacture, a dry cell paper liner having a coating comprising ungelatinized starch and a colloid binder.

2. As a new article of manufacture, a dry cell paper liner having a coating comprisin ungelatinized starch and a gelatlnized stare binder.

3. As a new article of manufacture, a dry cell paper liner having a coating comprising ungelatinized starch, and a mixed gelatinized starch and glue binder.

In testimony whereof I aflix my si nature.

WALTER B. SCHU TE.

allowed to set sufliciently so that the coating 7 hardens enough so that it may be handled. The setting usually results from the soaking of the water into the bibulous base. The starch ranules are held firmly together. by the col oid binder so that the coating does not dust or break ofl. The coated bibulous sheet is then introduced into the cell.

For dipping dry cell cores as described in the Staley co-pending application the preferred range is from 45% to 50% starch in a water solution containing from 0.5% to 1.5% of elatinized starch, preferably about 0.7%. T e suspending solution may contain dissolved ammonium chloride.

Throughout the specification the percentages given are based on the total final mixture of water, colloid, suspended starch and any other dissolved salts which may be added. Liquid suspension is used to desscribe a mobile fluid as distinguished from a pasty mass which could not be used for coating purposes by the dipping method. 

